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Renesis side port/peripheral port exhaust hybrid...
Naturally Aspirated Performance ForumDiscussion of naturally-aspirated rotary performance. No Power Adders, only pure rotary power!
From the "12A" to the "RENESIS" and beyond.
First, I think a rotary powered NC would be a hoot. Or an NA or NB frankly - I'd do the earlier ones personally - but a proper roadster with a rotary would be great.
Second, 250whp with a streetport 13B is possible. It's not easy or cheap but Dave Lemon of Mazdatrix apparently had one of his SCCA EProd engines in the 280 (flywheel) HP range with a Weber IDA and 42mm chokes (class rules) and I've heard tell that Rob Warcocki is making a couple HP off of 300 (at the flywheel) in his GT3 car (no induction restrictions)
The problem is you seem to be equating "street" port with some concept of street manners - smoothish idle, wide powerband, ability to accept mufflers.
This is a mistake.
I have not seen A/B dynos to prove this, but having built and driven EProd engines, it's going to be far more of a lightswitch powerband than bridgeports or peripheral ports. To get those sorts of power levels you need to optimize everything to an inch of its life, which means that the ports don't really have the gas velocity to work at low RPM, and frankly you're fighting for every bit of overlap you can get so it's not going to idle well either. Pretty much the only reason to build a street port engine like that is if you're not allowed to build a bridge or peripheral port.
If you poke around you can find the 13B-RE 1st gen RX-7 that Defined Autoworks made that's doing about 230hp at the wheels on a street port with a very well optimized (a lot of testing time in short) combination. I think that's about the limits before you're pushing things too far - fighting for that last 20hp is going to cost you. All that said though, I don't think 230hp at the wheels on an NC (or NB/NA) would be boring.
Thanks for that response man. I will do some digging around for that Defined Autoworks car and when the day comes to pull this build off, I may choose to enlist the help of a shop that's been there and done that before, depending on where I am from a time/money perspective.
As for the reference to street porting, I absolutely am looking at it from a "streetable" perspective and definitely do not want a powerband that's too narrow and an exhaust that's so loud I can't have a conversation. As I mentioned, I really want to have a car in the end that I can enjoy with my wife. Unfortunately, I planned on the FD being that car, but it's just too much...too loud, too stinky, too fast and too scary for her.
With all these things in mind, I just may need to stick to a stock Renesis for it's cleaner emissions...so it's not so stinky and unpleasant. Maybe that's the only way to achieve my goal of cool, roadster/date car or something along those lines. Hypothetically, if I were go catless with the franken-wankel that I mentioned before, and it was determined that the car was too much, let's say too stinky...could I put a catalytic converter in it and it do the job of cleaning it up enough to be pleasant?
That's the dyno/thread for the one I was mentioning.
In this day and age, you probably could put a good cat on and not lose too much power.
There's a place in England that has pioneered a way to weld the exhaust ports shut on the Renesis and put peripheral exhaust housings on - to be quite honest I want to try to duplicate that. I think though that even a relatively mild S5 NA engine (clean up street port, good tune, turbo rotor housings) or stock Renesis would be fun.
Just to add something to the thread, I stumbled upon some interesting style ports that are apparently illegal in SCCA racing, which I will not be doing so it doesn't matter to me. They appear to add a tremendous amount of overlap...?
The files are named Bridge, so I guess it's some kind of bridgeport, but I've never seen this style before. Will this port design cause reliability issues? Is this really a race only port?
This page has a bunch of "illegal" porting as far as the SCCA is concerned, but I wonder how much of it would be beneficial for guys like us -- weekend warriors...?
Thanks fellas!
Nick
Last edited by Brilliant7-LFC; 12-01-17 at 10:05 AM.
All of that stuff is trying to get around wording for an SCCA class that specifies "no bridge, no peripheral" porting; eventually SCCA had that document made to say that no, whatever the competitor says, that's still a bridge port and still illegal.
Exactly... the old wording for preventing bridge ports was something to the effect of "there must be only one contiguous port opening". So those cheater ports met the letter of the rules while still having a method of keeping the corner seals from falling out.
Dave Lemon at Mazdatrix petitioned the SCCA to change the wording to something like "air must not enter the engine beyond the track defined by the leading edge of the side seal". Which is a good definition of a street port that won't eat side seals. This better wording meets the actual intent of the old rule while also eliminating the loophole that allowed cheater bridges, comb ports, and the like,
i hate to be "that guy" but since the NC miata uses the Rx8 chassis, the 13B-MSP actually will bolt right in. the trans option, i think is an S2 Rx8 box with the NC tail housing, OR you could run the NC 6 speed with a Rotary bell housing on it. or if that all doesn't work, maybe you'd need to use the Rx8 trans and diff, with a shortened PPF and exhaust. (miata PPF is on the other side)
the wiring and engine control stuff is completely different between the NC and the Rx8, so it may be easiest to run a standalone ecu. plan B would be to use the Rx8 wiring harness, and rewire the whole NC.
should let you keep if not the stock AC compressor, at least the Rx8 one. Rx8 brakes and suspension go right onto the NC, it needs it too, somehow the Rx8 handling is magical, and the NC is awful.
if thats not enough, put GSL-SE rotor housings in the MSP, and then you get peripheral exhaust ports, and some power.
the Rx8 at 3000lbs is ok, but i have to think shaving ~500 pounds would just make everything better.
i hate to be "that guy" but since the NC miata uses the Rx8 chassis, the 13B-MSP actually will bolt right in. the trans option, i think is an S2 Rx8 box with the NC tail housing, OR you could run the NC 6 speed with a Rotary bell housing on it. or if that all doesn't work, maybe you'd need to use the Rx8 trans and diff, with a shortened PPF and exhaust. (miata PPF is on the other side)
the wiring and engine control stuff is completely different between the NC and the Rx8, so it may be easiest to run a standalone ecu. plan B would be to use the Rx8 wiring harness, and rewire the whole NC.
should let you keep if not the stock AC compressor, at least the Rx8 one. Rx8 brakes and suspension go right onto the NC, it needs it too, somehow the Rx8 handling is magical, and the NC is awful.
if thats not enough, put GSL-SE rotor housings in the MSP, and then you get peripheral exhaust ports, and some power.
the Rx8 at 3000lbs is ok, but i have to think shaving ~500 pounds would just make everything better.
Thanks for chiming in bud. I agree with basically everything you said. As for the PPF, I saw a thread where the RX-8 PPF was sectioned and shortened to fit the shorter NC chassis. The transmission and differential were the 8’s and the diff bolted right up, no modifications at all.
I have heard that the “suspension bolts up” as well. In theory does that mean I can just use an RX-8 subframe and factory mounts? Talk about easy! And if that’s the case, do I go full on and swap the control arms and everything else while I’m at it? I wonder if that would make a difference. Everything on the 8 is beefier which for the driveline is good but I’m not so sure I need extra beef and weight in the suspension...
I had discussed doing a Franken-Wankel earlier in the thread, using those peripheral housings with MSP rotors. Might go that route. If not, maybe just a stock Renesis.
Its all just dreams at the moment. I thought it was a cool idea and wanted to share with you guys and help me decide on what’s best.
Thanks to all of you who contributed. Now all I have to do is convince the wife...
i hate to be "that guy" but since the NC miata uses the Rx8 chassis, the 13B-MSP actually will bolt right in. the trans option, i think is an S2 Rx8 box with the NC tail housing, OR you could run the NC 6 speed with a Rotary bell housing on it. or if that all doesn't work, maybe you'd need to use the Rx8 trans and diff, with a shortened PPF and exhaust. (miata PPF is on the other side)
the Rx8 at 3000lbs is ok, but i have to think shaving ~500 pounds would just make everything better.
Regarding transmissions... the NC moved the PPF to the left side, same as the RX-8 which makes it simpler. NC transmission doesn't have a removable bellhousing (at least not the 6-speeds) same as the S2 RX-8 box. It should all bolt up with an NC PPF and driveshaft though.
https://www.rx8club.com/australia-ne...-build-158121/ Although that guy seems to say the NC PPF won't work as is. I'm not 100% clear he tried, and from being underneath both cars it looks to me like it *should* work.
Also, if you are just looking for a cool Mazda engined Miata swap and not hung up on rotary there is a gal in the UK that has done several Mazda K series V6 swaps into Miatas.
Little V6 revving out sounds good with those ITBs to my ear.
I was pondering a 1.8L K V6 with twin turbos in gutted RX-8 for a specific hillclimb class that allows 1.2L NA rotary, 2.5L NA piston or 1.8xL Piston forced induction (<--duh). Very stout little Aluminum block V6. Would lag for days though...
Yeah, I've seen that car on YouTube and have already told myself that I'd call Mazmart and speak with Paul about it one day. I appreciate you digging up the web page though because I couldn't find any information on the build itself. According to the page, it is using the RX-8 subframe. If that's the case, this swap becomes one of the simplest you could possibly ask for in any car!
Let's assume for a second you want to keep it simple and just swap over a stock Renesis and let's assume for a second you've found a wrecked RX-8 as a donor car (rear end damage of course). Simply swap over the subframe and front suspension complete, this eliminates any trouble with engine mounts and no custom work to fit the engine/transmission and suspension components. Like I stated before, the rear diff and rear subframe are all a match as well.
So, the only thing that needs any sort of modification and customization is the PPF, which you can section the RX-8 PPF and reinforce with additional welding, and the wiring of the car, which obviously won't be easy but should be doable. Consider that the car's share the same chassis and were built by the same company at the same time. You would assume that many of the factory wiring needs for both vehicles would be similar if not identical in some cases. You'd need custom lines for A/C, radiator and you'd need to adapt the hydraulic power steering pump from the Miata to the RX-8. Assuming you accomplish these relatively minor feats, you should be left with a like-factory RX-5 - or MX-8, or maybe RE-MX-5 or...well you guys come up with one.
As for the other options you mentioned, while it's cool to have a little revvy V6, that swap has never been done in an NC and even for an NA/NB it required far more fabrication than the RX-8 swap appears to need. The only other swap worth noting in my mind, is the 2.5L swap which is very common amongst the community right now. They take the 2.5L Ford/Mazda four cylinder from the Mondeo and swap it in. Apparently, you will be right around 210 bhp with this swap and the engine's are fairly common. For my money, the 13B-MSP is superior and more special, so the 2.5L swap does not sway me in the slightest.
The only thing which is appealing about the 2.5L swap is the fact it's been done umpteen times, which inherently means less guesswork and a more tried and test route.
Nick
Last edited by Brilliant7-LFC; 12-04-17 at 03:32 PM.
i hate to be "that guy" but since the NC miata uses the Rx8 chassis, the 13B-MSP actually will bolt right in. the trans option, i think is an S2 Rx8 box with the NC tail housing, OR you could run the NC 6 speed with a Rotary bell housing on it. or if that all doesn't work, maybe you'd need to use the Rx8 trans and diff, with a shortened PPF and exhaust. (miata PPF is on the other side)
I was going to go the other way, NC 5-speed with FB tailhousing in order to put a Duratec in the RX-7. But they never made an RX-8 with the smoothcase so nevermind. (I see some engine/trans combos on eBay from time to time that look like ribcase 5-speeds)
I have heard that the “suspension bolts up” as well. In theory does that mean I can just use an RX-8 subframe and factory mounts?
Nick
the NC miata is on the Rx8 chassis, so they share the subframe and control arms. basically the miata got smaller brake rotors, sway bars and the wrong spring/shock combination.
getting the 13B-MSP into the car is the easy part, getting it to run is the hard part
the NC miata is on the Rx8 chassis, so they share the subframe and control arms. basically the miata got smaller brake rotors, sway bars and the wrong spring/shock combination.
getting the 13B-MSP into the car is the easy part, getting it to run is the hard part
Exactly. My assumption would be that the wiring will be the most difficult to overcome while maintaining the every day driveability and retaining the creature comforts. Like I mentioned, I'm interested in a date car/fun weekend toy, but if my wife wanted to take it to work one day, I'd like for that to be a no brainer. Just drive it.
Having said all that, the cars are identical or near identical in so many ways and they're built by the same company, during the same era...could the wiring maybe be "easy"??
I'm thinking I'd definitely have to retain the RX-8 gauge cluster and PCM, but outside of that, I planned to use all the NC stuff outside of that. The RX-8 uses electric power steering and the NC, hydraulic - so that won't jive and I'll most probably always have a power steering light on the dash (unless I remove it). But, assuming I mount the NC power steering pump with a custom bracket, I should be in pretty good shape I'd think...?
Having said all that, the cars are identical or near identical in so many ways and they're built by the same company, during the same era...could the wiring maybe be "easy"??
If by easy you mean stripping both cars to the shell to remove the wiring harnesses and swapping all the RX-8 wiring harnesses onto the NC- then yes. Easy.
The harness you want on the NC is from the longer RX-8 so it should reach everything it needs to on the NC.
If by easy you mean stripping both cars to the shell to remove the wiring harnesses and swapping all the RX-8 wiring harnesses onto the NC- then yes. Easy.
The harness you want on the NC is from the longer RX-8 so it should reach everything it needs to on the NC.
HAHA...yeah I mean maybe you're right. I am not accustom to modern vehicles as much but say I used a standalone, I could in theory just leave the NC harness in the car and simply wire up the engine and the inputs from A/C compressor and whatever else to the standalone for idle control, for example. Perhaps in this manner I can avoid the need to use the factory RX-8 cluster...? I read that an RX-8 needs the cluster to start, period. You can't start it up without the factory cluster, but I would imagine that using a standalone with the requiste control for the OMP, factory knock sensor..ah la Haltech Elite 1500, this should be doable right?
But then we've got the intake manifold...and all the little motors...Haltech or Motec perhaps...getting pricey...
HAHA...yeah I mean maybe you're right. I am not accustom to modern vehicles as much but say I used a standalone, I could in theory just leave the NC harness in the car and simply wire up the engine and the inputs from A/C compressor and whatever else to the standalone for idle control, for example. Perhaps in this manner I can avoid the need to use the factory RX-8 cluster...? I read that an RX-8 needs the cluster to start, period. You can't start it up without the factory cluster, but I would imagine that using a standalone with the requiste control for the OMP, factory knock sensor..ah la Haltech Elite 1500, this should be doable right?
But then we've got the intake manifold...and all the little motors...Haltech or Motec perhaps...getting pricey...
Nick
Adaptronic just made a PNP rx8 ecu that will control the whole intake manifold and everything. It even connects to the factory dash and electric power steering. check it out.
Adaptronic just made a PNP rx8 ecu that will control the whole intake manifold and everything. It even connects to the factory dash and electric power steering. check it out.
That's great info dude, thank you for posting that! This may be the best option...unless I can figure out the stock wiring. Modern cars today have separate computers for separate functions. So, there's most probably a PCM, BCM, SRS module and ABS module in both of the cars. My feeling is, if I removed the PCM from the RX-8 and installed it into the MX-5 and wired up the Renesis just the same as if it were in the RX-8 chassis, that I could simply leave the BCM and ABS module alone as they don't really cross-communicate much, if at all. For that reason, when you scan the OBD II you don't have a P code show up when you're scanning the BCM, or vice versa, right?
So, without having done ANY engine swaps before, that is my thinking -- admittedly, this could be very flawed logic.
But, if I'm correct, then all of these computers should operate autonomously, leaving the PCM to do the bulk of the work in the swap.
The cluster is going to be the biggest hurdle and ensuring that it's receiving the signals it's supposed to be receiving from these various control modules. My expectation would be that the signal's will be identical in many cases being that these cars are virtually identical in a physical respect. Obviously the PCM's will differ because they use different engines, but my guess would be that to save cost, Mazda chose similar, if not identical components for other control systems in the vehicle.
Ideally, I'd pick up an S2 RX-8 that's been crashed and a NC3 Miata with a blown engine and use the 8 as a donor. Gauge cluster swap, seat swap, engine, transmission, differential, axles, and PPF to be transferred over with relative ease. From there, sell the rest of the 8's interior, brakes, suspension and body panels and junk it. Maybe I can make back a grand or so from that and use it to purchase a BBK. to spice it up a little bit and what not.
1. a lot of the things like switches and lights are the same, or very similar between the Rx8 and the NC, so maybe its easiest to just use the whole rx8 harness, and just change stuff to fit (like shorten it).
2. its possible that the two cars do use the same, or very similar controls, and then it would just be a matter of integrating the Rx8 ecu and wiring into the NC. structurally this isn't too hard, the Rx8 engine and PCM are fairly self contained. the Adaptronic probably makes this easier
if you spent a lot of time doing homework, studying the manuals, the answers are there.
The 2009+ RX8 S2 ecu & wiring is different from the 2004-2008 S1. The new Adaptronic RX8 modular ecu is only for the earlier S1 version. However, you can use the universal Adaptronic M2000 or M6000 modular ecu instead, but you have to make your own boomslang harness and add a module or two to get to the S1 equivalent setup.
The 2009+ RX8 S2 ecu & wiring is different from the 2004-2008 S1. The new Adaptronic RX8 modular ecu is only for the earlier S1 version. However, you can use the universal Adaptronic M2000 or M6000 modular ecu instead, but you have to make your own boomslang harness and add a module or two to get to the S1 equivalent setup.
I had considered the S2 because of the improvements with the OMP, but if I'm doing a standalone, I may as well run an external reservoir and use a SOHN adapter and simply run the OMP that way with an S1 engine. In truth, I don't know much about those adapters, just that I've read you need one to run an external reservoir, which I'm keen on doing. I'd much prefer to top off a reservoir with clean oil and maybe premix a bit than use crankcase oil that's already been through hundreds of heat cycles.
Other than the oil system being slightly different, the S2 and S1 are basically the same, right?
In all honesty, I'm leaning towards attempting to use the factory PCM due to cost. The wiring will be a challenge no question but a standalone and harness will most probably cost me in excess of $1,500 which is a fair amount to spend on this project. I may have to do it but hey it's worth a shot.
In truth, this project is nowhere near getting started but I wanted to get some information together to find out if it was even remotely doable and I'm pleasantly surprised to find so many of you are interested in it enough to lend your expertise. Thanks to you guys. What I'm hoping to do is convince my wife to go with it. I will need to beg, barter and probably bribe my way into this. And if that fails, perhaps a maintenance dose of a mind control med that I can slip her nightly...
Of course she told me: "If you selll the RX-7, no problem!" but I ain't selling my 7! So I gotta figure something else out. Any ideas there? lol
I'm reviving this thread and taking it another direction: highest power, OEM port
I'm tossing the idea around of a REW/MSP hybrid for the rally car - due to classing and license requirements stock port is restricted (but rotors aren't restricted...) unless I move to other class which I can't/don't want to at the moment.
Basic plan is to run REW front/rear irons but use the Renesis center iron given the intake port on it is so much bigger it is like a large streetport, however there are a few limitations/hurdles:
1. Coolant O-rings are in the housings on the MSP and will need the grooves to be machined into the center iron.
2. Rx8 rotors must be used due to exhaust port on center iron (thanks Pete)
3. Rx8 rotors require machining for tall 2mm apex seals to be used in a peripherial ported engine.
4. After machining requires balancing
5. Might as well clearance the rotors while I'm in there before its balanced...
I live near Chips Motorsports so all of this machining is feasible per him (but at what cost??? $$$$$$$$$$$) still a TBD discussion with him at the moment.
With this setup I can run s4 or s5 rotor housings (much cheaper and easier to come by) and will be a smaller exhaust port which would be beneficial with the added center iron exhaust port. S6 is always an option too but the cost jumps up and maybe I'm going to have too large of exhaust port.
External Issues:
1. New custom exhaust (needs one anyways really...)
2. Create engine mounts due to new center iron.
3. Re-program the haltech
4. Intake manifold
5. fuel rail (already have -AN setup so adapting will be easy)
The intake manifold is the biggest part of this as they are amidst of an organization merger and rule change/overhaul and with this action it will allow intake manifold/throttle bodies to be un-restricted in the class. With that you can really get the benefit of the larger ports as the s4 or s5 NA manifold will really limit the power to about ~8k
Observation:
Is it feasible? I don't see why not but at what cost do I not just run a REW block with existing S5 NA rotating and rx8 e-shaft/stat gear setup the car's engine currently runs. The engine mount portion would be easier and the overall cost would be drastically less then the real question is how much of this power is worth the extra money for that class? Its hard to guess the power output without actually doing it...
Future opportunity?:
I go ahead with this crazy plan and compete long enough with it to jump to the other class so then all I have to do to prep for that faster class is disassemble the engine, bridgeport and carbon apex seals and we can spin this ****** to ~11k and make all sorts of fun noises in the woods. With all the large ports and rotor work done it would be a great basis for any future porting/mods.
also a quick observation above with the balancing of rx8 rotors you need to be careful if the MSP front counterweight will work on an Rx7 front iron as it is more sunken in. I have not verified clearance on this yet otherwise I would use an S5 or S6 front counterweight as the rotating assembly will be balanced anyways you will be messing with the masses of both of the counterweights likely.
11-30-17, 01:09 PM
